Antioxidant Properties Of Flavonoids Research Articles

Flavonoids from Verbascum thapsus Protect Against Nephrotoxicity in Rats

General Background: Nephrotoxicity induced by carbon tetrachloride (CCl4) poses significant health risks, prompting the exploration of natural antioxidants for renal protection. Specific Background: Verbascum thapsus, a plant known for its flavonoid content, has shown potential in mitigating oxidative stress, but its specific protective effects against CCl4-induced nephrotoxicity remain under-investigated. Knowledge Gap: While previous studies have indicated antioxidant properties of flavonoids, their efficacy in renal preservation in vivo has not been fully elucidated. Aims: The study evaluated the antioxidative and nephroprotective properties of flavonoids from Verbascum thapsus leaves in a rat model of CCl4-induced nephrotoxicity.Results: Rats were divided into three groups: control, CCl4-treated, and flavonoid plus CCl4-treated. Biochemical analyses revealed that CCl4 significantly elevated malondialdehyde (MDA), urea, creatinine, and uric acid levels while decreasing superoxide dismutase (SOD) and glutathione (GSH) levels. Notably, flavonoid administration markedly reduced MDA, urea, creatinine, and uric acid levels and enhanced SOD and GSH levels compared to the CCl4-only group. Novelty: This study uniquely highlights the protective role of flavonoids from Verbascum thapsus against nephrotoxicity, demonstrating both their antioxidative capacity and renal preservation in an experimental model. Implications: The findings support the potential use of Verbascum thapsus as a therapeutic agent in the management of kidney diseases, suggesting further investigation into its application in clinical settings to address nephrotoxicity and related renal disorders. Highlights: Nephroprotective: Flavonoids significantly protect against CCl4-induced kidney damage. Biochemical Enhancement: Improved antioxidant levels; reduced harmful biochemical indicators. Therapeutic Potential: Supports natural treatments for kidney diseases. Keywords: Verbascum thapsus, flavonoids, nephrotoxicity, antioxidants, carbon tetrachloride

The influence of prolonged but low intensity blue light on the physiological properties of root tubers and the accumulation of flavonoids in Tetrastigma hemsleyanum Diels et Gilg

Tetrastigma hemsleyanum Diel et Gilg is a perennial herbaceous plant native to subtropical China with multiple medicinal applications. Supplementing with low-density blue light (BL) for 45 days (3 h/day) can not only significantly increase the yields of root tubers but also significantly increase the flavonoid content and its antioxidant activity. The chlorophyll content in the leaves of T. hemsleyanum significantly decreased, but the photosynthetic efficiency significantly increased after reaching the light saturation point. The production rate of superoxide anion radical in the leaves reached the highest peak after 1.5 h in BL and decreased at 3 h. The H2O2 content in the leaves decreased significantly, while the H2O2 content in the root tubers increased significantly at 3 h in BL. The objective of this research was to determine how the scavenging system, including antioxidant enzymes, antioxidants, and flavonoids respond to the oxidative stress induced by BL in root tubers. After exposure to BL, significant differences in the activity of APX and SOD were observed in the leaves and tubers within 3 h. By analyzing the upregulated flavonoids metabolites and key genes in metabolic pathways through the combined analysis of the flavonoid metabolic group and transcriptome in the root tubers, the upregulated accumulation of flavanols was found to be the main reason for the improvement in the antioxidant properties of flavonoids.

Mucosal Adhesive Chitosan Nanogel Formulations of Antibiotics and Adjuvants (Terpenoids, Flavonoids, etc.) and Their Potential for the Treatment of Infectious Diseases of the Gastrointestinal Tract.

Bacterial infections are usually found in the stomach and the first part of the small intestine in association with various pathologies, including ulcers, inflammatory diseases, and sometimes cancer. Treatment options may include combinations of antibiotics with proton pump inhibitors and anti-inflammatory drugs. However, all of them have high systemic exposure and, hence, unfavorable side effects, whereas their exposure in stomach mucus, the predominant location of the bacteria, is limited. Chitosan and nanogels based on chitosan presumably are not absorbed from the gastrointestinal tract and are known to adhere to the mucus. Therefore, they can serve as a basis for the local delivery of antibacterial drugs, increasing their exposure at the predominant location of therapeutic targets, thus improving the risk/benefit ratio. We have used E. coli ATCC 25922 (as a screening model of pathogenic bacteria) and Lactobacilli (as a model of a normal microbiome) to study the antibacterial activity of antibacterial drugs entrapped in a chitosan nanogel. Classical antibiotics were studied in a monotherapeutic regimen as well as in combination with individual terpenoids and flavonoids as adjuvants. It has been shown that levofloxacin (LF) in combination with zephirol demonstrate synergistic effects against E. coli (cell viability decreased by about 50%) and, surprisingly, a much weaker effect against Lactobacilli. A number of other combinations of antibiotic + adjuvant were also shown to be effective. Using FTIR and UV spectroscopy, it has been confirmed that chitosan nanogels with the drug are well adsorbed on the mucosal model, providing prolonged release at the target location. Using an ABTS assay, the antioxidant properties of flavonoids and other drugs are shown, which are potentially necessary to minimize the harmful effects of toxins and radicals produced by pathogens. In vivo experiments (on sturgeon fish) showed the effective action of antibacterial formulations developed based on LF in chitosan nanogels for up to 11 days. Thus, chitosan nanogels loaded with a combination of drugs and adjuvants can be considered as a new strategy for the treatment of infectious diseases of the gastrointestinal tract.

The role of redox active copper(II) on antioxidant properties of the flavonoid baicalein: DNA protection under Cu(II)-Fenton reaction and Cu(II)-ascorbate system conditions

The antioxidant properties of flavonoids are mediated by their functional hydroxyl groups, which are capable of both chelating redox active metals such as iron, copper and scavenging free radicals. In this paper, the antioxidant vs. prooxidant and DNA protecting properties of baicalein and Cu(II)-baicalein complexes were studied under the conditions of the Copper-Fenton reaction and of the Copper-Ascorbate system. From the relevant EPR spectra, the interaction of baicalein with Cu(II) ions was confirmed, while UV–vis spectroscopy demonstrated a greater stability over time of Cu(II)-baicalein complexes in DMSO than in methanol and PBS and Phosphate buffers. An ABTS study confirmed a moderate ROS scavenging efficiency, at around 37%, for both free baicalein and Cu(II)-baicalein complexes (in the ratios 1:1 and 1:2). The results from absorption titrations are in agreement with those from viscometric studies and confirmed that the binding mode between DNA and both free baicalein and Cu-baicalein complexes, involves hydrogen bonds and van der Waals interactions. The DNA protective effect of baicalein has been investigated by means of gel electrophoresis under the conditions of the Cu-catalyzed Fenton reaction and of the Cu-Ascorbate system. In both cases, it was found that, at sufficiently high concentrations, baicalein offers some protection to cells from DNA damage caused by ROS (singlet oxygen, hydroxyl radicals and superoxide radical anions). Accordingly, baicalein may be useful as a therapeutic agent in diseases with a disturbed metabolism of redox metals such as copper, for example Alzheimer's disease, Wilson's disease and various cancers. While therapeutically sufficient concentrations of baicalein may protect neuronal cells from Cu-Fenton-induced DNA damage in regard to neurological conditions, conversely, in the case of cancers, low concentrations of baicalein do not inhibit the pro-oxidant effect of copper ions and ascorbate, which can, in turn, deliver an effective damage to DNA in tumour cells.

IN VITRO ANTIOXIDANT AND ANTIMICROBIAL ACTIVITIES OF ISOLATED FLAVONOID FROM METHANOLIC EXTRACT OF ANDROGRAPHIS ECHIOIDES LEAVES

The objective of this investigation was to identify the active flavonoid present across the entire Andrographis echioides plant. Using a methanolic extract from the leaves of Andrographis echioides, it was examined how flavonoids may be isolated from a plant component. Phytochemical analyses revealed the presence of flavonoid components in methanol extract. The recovered flavonoid component was further purified by column chromatography and TLC. The structures of the isolated compounds were characterized using UV-visible, FT-IR, 1H & 13C NMR and mass spectroscopy. This led to the isolated compound being given the name 9-methoxy-6a,11a-dihydro-6H-benzofuro[3,2-c]chromen-3-ol or medicarpin. Further biological investigation is needed for the isolated flavonoid discovered in this plant. Recent research has concentrated on the role of flavonoids as antioxidants when oxidative stress is present. The antioxidant properties of flavonoids were also discussed.

Sources and Chemistry of Flavonoids; their Biological and Therapeutic Potential

Flavonoids are natural polyphenolic compounds, which are responsible for the taste and colors of medicinal plants, herbs, fruits, vegetables. Fruits (e.g., Berries, cherries, plums, apples, lemons, oranges, and grapes etc) and vegetables (e.g., broad beans, olives, onions, spinach, shallot etc) are the main sources of flavonoids. They also exist abundantly in cocoa products, black and green tea, red wine, red pepper, chamomile, celery, parsley, ginkgo, and mint. Flavonoids derivatives can also be synthesized through esterification, halogenation, alkoxylation, alkylation, aromatic hydroxylation, acylation and conjugation with various organic compounds. Flavonoids can be supplemented in a staple of food as nutraceutical agents and have an important role in human diet. They possess diverse biological activities including anti-inflammation, anti-oxidation, anti-cancer, anti-diabetes, anti-obesity, antimutagenic, neuroprotective and also have beneficial effects on oxidative stress, inflammation, insulin resistance, lipid metabolism and neurodegenerative diseases (e.g., amyotrophic lateral sclerosis, Huntington’s disease, Parkinson’s disease and Alzheimer’s disease). Flavonoids contain a 15-carbon skeleton; the basic structure consists of a flavan nucleus, a combination of two benzene and one pyran rings. Flavonoids are divided into eight important groups i.e., flavones, flavanols, isoflavones, flavan-3-ols, flavanonols, anthocyanidins, chalcones, and flavanones. A structure-activity relationship exists between flavonoids and their antioxidant activities. Flavonoids are effective in chelating metal ions and scavenging free radicals. The antioxidant properties of flavonoids are governed by their –OH groups, differences in hydrophobicity and molecular planarity.

Evaluation of the Protective Effect of Salvia macrosiphon Boiss on the Serum Urea and Creatinine Levels in Renal Ischemia Reperfusion Injury

Background: Renal ischemia-reperfusion is known as the underlying pathophysiology of a variety of severe clinical disorders, such as acute renal failure. The use of antioxidants is one of the most important treatment strategies to reduce the ischemia-reperfusion induced injury due to the importance of reactive oxygen species and oxidative stress during ischemia reperfusion. Salvia spices, especially Salvia macrosiphon Boiss, are rich in antioxidant compounds. The present study aimed to investigate the protective effects of these substances on renal ischemia reperfusion. Materials and Methods: In this study, 42 Wistar rats were divided into six groups of seven animals per group. The groups included a sham, a control, and four treatments. One of the treatment groups was treated with luteolin, and the other three groups were treated with different concentrations (50, 100, 150 mg/kg) of Salvia macrosiphon Boiss methanolic extract for 20 days before ischemia. After 24 hours following ischemia, blood samples were taken from the rats, and their serum creatinine and urea levels were evaluated. Results: Salvia macrosiphon Boiss extract (at the dose of 100 mg/kg) significantly reduced urea and creatinine levels (P<0.001). Moreover, Luteolin decreased both ceratinine (P<0.01) and urea (P<0.05) levels. Conclusion: This study confirmed the positive and significant effect of Salvia macrosiphon Boiss extract and Luteolin on the studied factors. The observed effect could be in part due to the potential antioxidant properties of flavonoids and methanol extract of Salvia macrosiphon Boiss.

Recent Developments in Effective Antioxidants: The Structure and Antioxidant Properties.

Since the last few years, the growing interest in the use of natural and synthetic antioxidants as functional food ingredients and dietary supplements, is observed. The imbalance between the number of antioxidants and free radicals is the cause of oxidative damages of proteins, lipids, and DNA. The aim of the study was the review of recent developments in antioxidants. One of the crucial issues in food technology, medicine, and biotechnology is the excess free radicals reduction to obtain healthy food. The major problem is receiving more effective antioxidants. The study aimed to analyze the properties of efficient antioxidants and a better understanding of the molecular mechanism of antioxidant processes. Our researches and sparing literature data prove that the ligand antioxidant properties complexed by selected metals may significantly affect the free radical neutralization. According to our preliminary observation, this efficiency is improved mainly by the metals of high ion potential, e.g., Fe(III), Cr(III), Ln(III), Y(III). The complexes of delocalized electronic charge are better antioxidants. Experimental literature results of antioxidant assays, such as diphenylpicrylhydrazyl (DPPH) and ferric reducing activity power assay (FRAP), were compared to thermodynamic parameters obtained with computational methods. The mechanisms of free radicals creation were described based on the experimental literature data. Changes in HOMO energy distribution in phenolic acids with an increasing number of hydroxyl groups were observed. The antioxidant properties of flavonoids are strongly dependent on the hydroxyl group position and the catechol moiety. The number of methoxy groups in the phenolic acid molecules influences antioxidant activity. The use of synchrotron techniques in the antioxidants electronic structure analysis was proposed.

Isolation of Major Compounds and Gastroprotective Activity of Alchemilla Caucasica on Indomethacin Induced Gastric Ulcers in Rats.

The Alchemilla genus, which belongs to the Rosaceae family, is known as Lady's mantle and is commonly used in traditional medicine. This study was designed to investigate the major metabolites isolation and gastroprotective effects of Alchemilla caucasica. Phytochemical studies were carried out using column chromatography on Alchemilla caucasica. The gastroprotective effect of ethanol extract of this plant was tested on indomethacin-induced gastric ulcer model in rats. In addition, superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione (GSH) parameters in the stomach tissue were examined. Quercetin-3-O-glucuronide, apigenin, and catechin were isolated from aerial parts of Alchemilla caucasica. When macroscopic ulcer index and histopathological results were analyzed, the extract at 200 mg/kg dose was found to be most effective. All doses of extract reduced MDA level and enhanced SOD activity and GSH level. The results of this study showed that Alchemilla caucasica has significant antiulcer activity. This effect was thought to be caused by antioxidant properties of flavonoids.

Understanding the Composition, Biosynthesis, Accumulation and Transport of Flavonoids in Crops for the Promotion of Crops as Healthy Sources of Flavonoids for Human Consumption.

Flavonoids are a class of polyphenolic compounds that naturally occur in plants. Sub-groups of flavonoids include flavone, flavonol, flavanone, flavanonol, anthocyanidin, flavanol and isoflavone. The various modifications on flavonoid molecules further increase the diversity of flavonoids. Certain crops are famous for being enriched in specific flavonoids. For example, anthocyanins, which give rise to a purplish color, are the characteristic compounds in berries; flavanols are enriched in teas; and isoflavones are uniquely found in several legumes. It is widely accepted that the antioxidative properties of flavonoids are beneficial for human health. In this review, we summarize the classification of the different sub-groups of flavonoids based on their molecular structures. The health benefits of flavonoids are addressed from the perspective of their molecular structures. The flavonoid biosynthesis pathways are compared among different crops to highlight the mechanisms that lead to the differential accumulation of different sub-groups of flavonoids. In addition, the mechanisms and genes involved in the transport and accumulation of flavonoids in crops are discussed. We hope the understanding of flavonoid accumulation in crops will guide the proper balance in their consumption to improve human health.

The effects of flavonoids on human first trimester trophoblast spheroidal stem cell self-renewal, invasion and JNK/p38 MAPK activation: Understanding the cytoprotective effects of these phytonutrients against oxidative stress

Adequate invasion and complete remodelling of the maternal spiral arteries by the invading extravillous trophoblasts are the major determinants of a successful pregnancy. Increase in oxidative stress during pregnancy has been linked to the reduction in trophoblast invasion and incomplete conversion of the maternal spiral arteries, resulting in pregnancy complications such as pre-eclampsia, intrauterine growth restriction, and spontaneous miscarriages resulting in foetal/maternal mortality. The use of antioxidant therapy (vitamin C and E) and other preventative treatments (such as low dose aspirin) have been ineffective in preventing pre-eclampsia. Also, as the majority of antihypertensive drugs pose side effects, choosing an appropriate treatment would depend upon the efficacy and safety of mother/foetus. Since pre-eclampsia is mainly linked to placental oxidative stress, new diet-based antioxidants can be of use to prevent this condition. The antioxidant properties of flavonoids (naturally occurring phenolic compounds which are ubiquitously distributed in fruits and vegetables) have been well documented in non-trophoblast cells. Therefore, this study aimed to investigate the effects of flavonoids (quercetin, hesperidin) and their metabolites (Quercetin 3-O-β-glucuronide and hesperetin), either alone or in combination, on first trimester trophoblast cell line HTR-8/SVneo during oxidative stress. The data obtained from this study indicate that selected flavonoids, their respective metabolites significantly reduced the levels of reduced glutathione (p < 0.0001) during HR-induced oxidative stress. These flavonoids also inhibited the activation of pro-apoptotic kinases (p38 MAPK and c-Jun N-terminal kinase) during HR-induced phosphorylation. In addition, they enhanced spheroid stem-like cell generation from HTR8/SVneo cells, aiding their invasion. Our data suggest that dietary intake of food rich in quercetin or hesperidin during early pregnancy can significantly improve trophoblast (placenta) health and function against oxidative stress.

Inhibition of Lipoxygenase and Peroxidase Reaction by Some Flavonols and Flavones: The Structure-Activity Relationship

Some flavonoids were investigated for their effects on lipoxygenase and peroxidase. The strongest inhibitor of lipoxygenase was kaempferol with one hydroxyl group situated at the 4’ position in the B ring, with activity of 21.2±2.03 calculated per μmole of compound. The weakest inhibition was observed for diosmetin with a hydroxyl group at the 3′ position and a methoxyl group at 4′ in the B ring, with activity of 1.17±0.77 per μmole. Peroxidase was most strongly inhibited by quercetin (22.7±0.05) with two hydroxyl groups in the B ring at 3′ and 4′. The weakest inhibitor of peroxidase was genkwanin (0±0.16) with one hydroxyl group at position 4′ in the B ring and methoxyl at position 7 in the A ring. The correlation coefficient between reduction of Fe3+ by flavonoids and inhibition of lipoxygenase by these compounds was 0.72 and the reduction of Fe3+ and inhibition of peroxidase was 0.24. The results show that inhibition of peroxidase is weakly associated with reducing properties of phenols and inhibition of lipoxygenase may be associated with antioxidant properties of flavonoids.

Quantitative structure-Activity relationship model for antioxidant activity of flavonoid compounds in traditional Chinese herbs

There are many diseases related to the excessive amount of free radical in human body produced by various metabolic functions. The generation of free radicals can be controlled by the presence of antioxidants. One of the largest phytochemical groups in herbs which commonly exhibit antioxidant activity is flavonoid. The structure of flavonoid compounds can be represented by various types of descriptors generated by the DRAGON software. A series of flavonoids with their antioxidant activities values in 2,2'-Azinobis-3-ethylbenzothiazoline-6- sulphonic acid (ABTS) assays from traditional Chinese herbs is employed as the data set. The aim of the study is to develop reliable quantitative structure-Activity relationship also known as QSAR models of flavonoid compounds using the combination of forward stepwise as variable selection method and multiple linear regression (MLR) analysis. The suitable dimensional block of descriptors and significant descriptors that contribute to the antioxidant properties of flavonoids are identified. The performance of the QSAR models are reported as rcalc 2 and are validated using cross-validation (rcv 2 ), the external test set (rpred 2 ) and Y-randomisation (rr 2) to confirm the reliability of the model. Based on the findings, the developed models are robust and reliable and able to explain 78 % variance of antioxidant activity. From the QSAR models, two selected descriptors that significantly affect the antioxidant activity are topological indices (PW5) and 2D-Autocorrelations (JGI4). Both of them belong to the 2-dimensional (2D) block of descriptors. This finding proves that the simpler 2D descriptors appear to be sufficient and beneficial information and perform better in building predicted model than 3D descriptors.

Antioxidant Properties of Flavonoids and Honeys Studied By Optical Spectroscopy Methods

Flavonoids are considered very efficient radical scavengers and found in almost every plant. Antioxidant activities of flavonoids and a few popular kinds of bee honeys were investigated using absorbance spectroscopy. Spectral methods are powerful tools for the study of biologically active compounds and allow measurements of low concentrated substances under physiological conditions. Quercetin, naringenin, catechin, 3-hydroxyflavone were studied during the reaction with the 2,2-diphenyl-1- picrylhydrazyl radical (DPPH·). The results suggest that quercetin and catechin are better antioxidants than vitamin C. Among the analyzed honeys buckwheat honey exhibited the strongest antioxidant properties. Kinetic studies of the radical-scavenging activity were also performed. One can observe that popular vitamin C reduces free radicals instantly after adding to the solution, while flavonoids cause rather an exponential decay in concentration of the free radicals in the solutions. Our results show that adding of CuCl 2 to the solution of DPPH and quercetin did not influence the level of antioxidant capacity of quercetin.

Antioxidant Properties of Flavonoids and Honeys Studied By Optical Spectroscopy Methods

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In Vitro Antioxidant Properties of Flavonoids and Polysaccharides Extract from Tobacco (Nicotiana tabacum L.) Leaves

In the present study, antioxidant properties of flavonoids and polysaccharides from tobacco (Nicotiana tabacum L.) leaves were evaluated in several in vitro systems, e.g., scavenging activities on hydroxyl, superoxide anion, 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radicals, and reducing power. Flavonoids showed much better activity than polysaccharides in scavenging activities on free radicals. When compared to the positive control, ascorbic acid, both showed weaker antioxidant potential. However, flavonoids possessed comparable superoxide anion, DPPH and ABTS radical scavenging abilities to ascorbic acid at high concentration (600 μg/mL). Meanwhile, it was found that flavonoids had prominent effects on the reducing power, which was equivalent to ascorbic acid, and was significantly higher than polysaccharides. These results clearly indicate that flavonoids are effective in scavenging free radicals and have the potential to be powerful antioxidants. Thus, tobacco leaves could be considered as a potential source of natural antioxidants for food, pharmaceutical, cosmetics or nutraceutical industries.

Concentration Dependent Effect of (−)‐Epicatechin on Na+/K+‐ATPase and Ca2+‐ATPase Inhibition Induced by Free Radicals in Hypertensive Patients: Comparison with L‐ascorbic Acid

Although the antioxidant properties of flavonoids are well documented, it is still unclear whether these effects are dependent on radical scavenging or iron chelating activities. Oxidative stress, a state of excessive reactive oxygen species (ROS) activity, is associated with vascular disease conditions such as hypertension. Both the anti- and pro-oxidant effects of tea catechins have been implicated in the alterations of cellular functions that determine their chemoprotective and therapeutic potentials in health and diseases. The present study examined the concentration dependent (10(-7) to 10(-4) m) effects of (-)-epicatechin and L-ascorbic acid on Na(+) /K(+) -ATPase and Ca(2+) -ATPase activity in hypertensive patients and normal subjects. L-ascorbic acid has been used as a positive control to compare the effect of (-)-epicatechin. A significant (p < 0.0001) decrease in the activities of Na(+) /K(+) -ATPase and Ca(2+) -ATPase was observed in hypertensive patients compared with normal subjects. We report that (-)-epicatechin shows a significant (p < 0.001) dose-dependent protective effect against oxidative stress induced by tert-butyl hydroperoxide (t-BHP), which is manisfested as a decrease in the activity of erythrocyte Na(+) /K(+) -ATPase and Ca(2+) -ATPase, in hypertensive patients as well as normal subjects. The effect of L-ascorbic acid was also significant (p < 0.001) and was comparable with that of (-)-epicatechin.

Theoretical investigation of the effect of sugar substitution on the antioxidant properties of flavonoids

Natural flavonoids are secondary phenolic plant metabolites known for their bioactivity as antioxidants. The evaluation of this property is generally done by the estimation of their direct free radical-scavenging activity as hydrogen or electron donating compounds. This paper reviews experimental results available in the literature for a selection of flavonoids and compares them with calculated quantities characteristic of the hydrogen or electron donation. For that purpose, bond dissociation energies, ionization potentials and electron transfer enthalpies are computed by using DFT methods and the ONIOM procedure implemented in the ab initio program Gaussian. This process has been chosen because it can be extended to the study of large molecules. When acid dissociation and interaction with the solvent are taken into account, the results present very good concordance with experimental results, enlightening the complexity of the processes involved in the classical assays which measure the ability of compounds to scavenge the (2,2′-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt) radical cation (ABTS +) or the 2,2-diphenyl-1-picryl-hydrazyl radical (DPPH·). This study demonstrates the good accuracy of theoretical calculations in obtaining the relative energies involved in free radical scavenging abilities and its capacity for predictive behaviour. It also highlights the necessity to take into account the pKa of the compounds and the solvent interaction. The ability of the method to calculate the antioxidant properties of larger molecules are tested on glycosylated flavonoids and the effects of sugar substitution on the antioxidant properties of flavonoids are investigated, pointing out the importance of the charges on the oxygen atoms.

Antioxidative Properties of Flavonoids

Evidence accumulates that a family of plant compounds, known as flavonoids, can prevent or slow down the progression of cardiovascular diseases, cancer, inflammatory and neurodegenerative diseases. Flavonoids are considered beneficial, this is often attributed to their powerful antioxidant properties. In this role, certain types of flavonoids are considered to be far more powerful than the two most common antioxidants, vitamin C and vitamin E, at preventing cellular damage brought on by free radicals. Interestingly, flavonoids exert those activities not only through direct radical scavenging, but also through regulating nitric oxide, and chelating metals. In addition, flavonoids are thought to facilitate/promote other important biological processes, resulting in modulation of enzymes, a decrease in leukocyte immobilization, inhibition of cell proliferation and angiogenesis, and effects on signaling pathways. The results of in vitro studies have demonstrated that the antioxidative property of flavonoids is unambiguous; however it is still not supported by strong consistent evidence in vivo. Therefore, the antioxidant theory as a mechanism of action of flavonoids is controversial. As a result, flavonoids are hypothesized to exert their activities partly through cell signaling pathways. This review intends to acquaint the reader with different pathways in which flavonoids function or might function. Furthermore, we will provide insight into the beneficial health effects of these substances

Effect of dark chocolate on plasma epicatechin levels, DNA resistance to oxidative stress and total antioxidant activity in healthy subjects

Dark chocolate (DC) may be cardioprotective by antioxidant properties of flavonoids. We investigated the effect of DC (860 mg polyphenols, of which 58 mg epicatechin) compared with white chocolate (WC; 5 mg polyphenols, undetectable epicatechin) on plasma epicatechin levels, mononuclear blood cells (MNBC) DNA damage and plasma total antioxidant activity (TAA). Twenty healthy subjects followed a balanced diet (55 % of energy from carbohydrates, 30 % from fat and 1 g protein/kg body weight) for 4 weeks. Since the 14th day until the 27th day, they introduced daily 45 g of either WC (n 10) or DC (n 10). Whole experimental period was standardised in antioxidant intake. Blood samples were collected at T(0), after 2 weeks (T(14)), 2 h and 22 h after the first chocolate intake (T(14+2 h) and T(14+22 h)), and at 27th day, before chocolate intake (T(27)), 2 h and 22 h after (T(27+2 h) and T(27+22 h)). Samples, except for T(14+2 h) and T(27+2 h), were fasting collected. Detectable epicatechin levels were observed exclusively 2 h after DC intake (T(14+2 h) = 0.362 (se 0.052) micromol/l and T(27+2 h) = 0.369 (se 0.041) micromol/l); at the same times corresponded lower MNBC DNA damages (T(14+2 h) = - 19.4 (se 3.4) % v. T(14), P < 0.05; T(27+2 h) = - 24 (se 7.4) % v. T(27), P < 0.05; T(14+2 h) v. T(27+2 h), P = 0.7). Both effects were no longer evident after 22 h. No effect was observed on TAA. WC did not affect any variable. DC may transiently improve DNA resistance to oxidative stress, probably for flavonoid kinetics.